A combination of intracellular and extracellular recording methods will be used in vertebrate retinas, mainly isolated eye cup preparations from cold-blooded vertebrate retinas. This work will be directed mainly toward three closely overlapping problem areas as follows: (1) Processes underlying the excitation of vertebrate rods and cones. (2) Interactions between receptors that influence receptor potentials and the detailed mechanisms underlying such interactions. (3) Physiology of the pigment epithelium and functional relations between the pigment epithelium and neural retina.